A Reichert-Jung cryofract 190 machine, which allows the efficient preparation of freeze-fracture, freeze-etch, and surface-replica materials for examination by transmission electron microscopy, is requested. This machine would replace a heavily used 16-year-old Balzers 360 M and would allow preparation of tissue in 15 min that now requires a minimum of 2.5 hr per specimen. The new instrument also has features necessary for ongoing research endeavors, such as a double fracture device, a replica thickness monitor control, a stage and rotor for rotary shadowing, and temperature control equipment for deep etching. The Principal Investigator, Dr. Daniel Friend, has used freeze-fracture methodology productively since the early 1970's. He has explored variations of sperm membrane during epididymal maturation and changes prior to fertilization. He has also introduced the use of filipin as a freeze-fracture cytochemical method to detect membrane sterols. His major goal now is to apply recent developments in freeze-fracture immunocytochemistry and monoclonal antibodies to map at high resolution the immunogenic glycolipids and proteins of sperm, RBC, and transporting epithelia. Dr. Dorothy Bainton, who studies the differentiation and function of bone marrow cells, will study by surface replica and immunocytochemistry the redistribution of glycoproteins induced by thrombin activation on intact platelets, and perform similar studies on neutrophils stimulated with chemotactic substances. Dr. D. Papahadjopoulos, who studies membrane fusion events using liposomes, will use the equipment to study the representation of fusogenic proteins as intramembranous particles and their role in membrane fusion. Dr. David Phillips, who pioneered studies on platelet plasma membrane glycoproteins, and has previously characterized the morphology of the isolated GPIIb-IIIa complex, will now be able to study the structre of ligand-receptor complexes by rotary shadowed images and their relationship to platelet cytoskeleton. Dr. Joan Fox will be able to expand her studies on the contractile proteins of platelets. In addition to the PI's, these investigators have the capable help of three research associates (Hsieh, Isenberg, and Boyles) who have years of experience with these procedures. Acquisition of this instrument will allow an increase in the pace of progress of ongoing work, and allow several investigators to explore new areas.